1. Field of the Invention
The present invention relates generally to a mechanical sealing device for preventing fluid leakage, which is additionally installed at a position around each of interior and exterior sealing units which are mounted at both sides of a power drive unit so as to prevent fluid from leaking out of a shaft rotatably installed on the sidewall of a fluid tank containing fluid, such as gas or liquid, thus accomplishing a double-sealing effect. More particularly, this invention relates to a mechanical sealing device for preventing fluid leakage, which forms a sealing chamber by means of a flange, a seal casing and a seal cover at a position outside a gland ring used for holding the gland packings installed in a stuffing box, and which is provided in the sealing chamber with both a rotary sealing ring fixed to a sleeve and a stationary sealing ring positioned to come into contact with both the sleeve and the rotary sealing ring, and in which the stationary sealing ring is held by a spring-biased slip ring, and which also has additional sealing rings brought into contact with the sleeve at the inner surfaces of the gland ring and the seal cover.
2. Description of the Prior Art
Recently, as the natural environment is excessively contaminated, environmental pollution, including air pollution, is considered as an important social problem. Above all, gas produced from nitric-acid slurry is worse than other contaminants, due to its offensive odor.
Thus, in order to prevent environmental pollution caused by fluid leakage, there has been proposed a mechanical sealing device, which serves to prevent fluid from leaking out of a shaft that is rotatably installed to a fluid tank containing fluid, such as gas or liquid, and is rotated by a power drive unit. The conventional sealing device will be described with reference to FIGS. 1 to 3.
A hole 1-1 is formed through the sidewall of a fluid tank 1 such that a first shaft 2 is inserted into the hole 1-1. A support plate 1-2 is mounted to the sidewall of the tank 1 at a position around the hole 1-1. A plurality of bolt rods 1-3 are set in the support plate 1-2 at regular intervals. The first shaft 2 to which a power drive unit 30 is mounted is inserted into the hole 1-1. A second shaft 2-1 of a pipe shape is coupled to an end of the first shaft 2 exposed to the outside of the power drive unit 30.
That is, the first and second shafts 2 and 2-1 are provided at both sides of the power drive unit 30, respectively. An interior sealing unit 31 is installed on the first shaft 2, while an exterior sealing unit 32 is installed on the second shaft 2-1.
A sleeve 3 is fitted over each of the first shaft 2 of the interior sealing unit 31 and the second shaft 2-1 of the exterior sealing unit 32. Two stuffing boxes 6 are installed to the outer surfaces of the two sleeves 3 such that the first stuffing box 6 of the interior sealing unit 31 is opposite to the second stuffing box 6 of the exterior sealing unit 32. In this case, each of the two stuffing boxes 6 is provided with a plurality of gland packings 5. A flange 6-1, mounted to the stuffing box 6 of the interior sealing unit 31, is mounted to the support plate 1-2 by the bolt rods 1-3, thus being mounted to the fluid tank 1, with nuts 1-4 tightened to the bolt rods 1-3. Meanwhile, a support frame 35 is mounted to the stuffing box 6 of the exterior sealing unit 32, with a bearing 36 interposed between the frame 35 and said stuffing box 6. In the interior sealing unit 31 constructed in this way, the sleeve 3 is rotated along with the shaft 2 by power generated from the power drive unit 30, in the stop mode of the fluid tank 1, the stuffing box 6 and the gland packings 5. In the exterior sealing unit 32, the stuffing box 6 is rotated together with the gland packings 5, in the stop mode of the shaft 2-1, the shaft 2 and the sleeve 3.
However, such a conventional sealing device has a problem that fluid easily leaks out from the shaft, because the device is designed in such a way that its interior and exterior sealing units 31 and 32 perform a sealing function using only the gland packings 5, so the device cannot fulfill a complete sealing function in the case where the contact surfaces of the gland packings 5 and the sleeves 3 are worn. The conventional sealing device may thus cause air pollution, due to toxic gas produced by fluid, and spread offensive odor when there occurs fluid leakage. The toxic gas may do harm to the health of local inhabitants.
Further, when the gland packings 5 and the sleeves 3 are worn to reduce the sealing function of the sealing device, they must be replaced with new ones. But, since the gland packings 5 and the sleeves 3 are heavy, it is not easy to replace them with new ones, and besides, it takes a long time to replace them with new ones. In addition, the conventional sealing device has other problems that downtime is prolonged due to frequent replacement work, and the repair cost of the device is high.